Distal radius fractures are among the most common encountered fractures in emergency departments of hospitals. Usually they are referred to as Colles or Pouteau fractures. The frequency of report is about 10% of all fractures. The most common cause of this fracture are a fall on the outstretched hand, a fall from height and motorvehicle accidents. The classic method of treatment is closed reduction of the fracture and plaster cast support. However, plaster cast is only sufficient for fractures with no or little displacement and/or comminution. Other treatment possibilities include open reduction and plate osteosynthesis, functional bracing and external fixation. External fixation is mainly applied in comminuted, intra-articular and/or unstable fractures. The management of distal radius fractures by means of external fixation is based on the principle of ligamentotaxis. This means that when a force is applied across a joint (e.g. the wrist) by distraction, the capsule and ligaments of the joint are placed under tension and thus tend to maintain the reduction of the adjacent bone fragments.
The conventional external fixation devices consist of a rigid frame built up from two proximal pins (e.g. Kirschher wires) in the radius and two distal pins in the second and/or third metacarpal, connected by one or more cross bars. Since this configuration of the frame crosses the wrist joint, no movement of this joint is possible in presence of the external fixator. This can result in severe complications like post-traumatic joint arthrosis, reflex sympathetic dystrophy (Sudeck's dystrophy) and osteoporosis, leading to impairment of wrist function and further morbidity.
From EP-A1 0 458 486 RICHARDSON a bone fixator frame is known which allows relative rotation of the bone segments in two axes. Similar single axis frames have been used for the fixation of radius fractures. These known fixators do not allow for physiological range of movement and require less than optimal surgical approach.